The ratings agency Standard & Poor's is threatening to downgrade the credit rating of 15 euro zone countries.
S&P said it may take the action because of growing "systemic stresses" in the euro zone in recent weeks. It also cited the failure of European leaders to come up with an adequate plan to address the crisis.
Six countries, including Germany, could see their top credit ratings of AAA knocked down by one notch. The other nine, including AAA-rated France, could see their ratings brought down two notches.
Cyprus was already on downgrade watch and Greece already has a 'junk' CC-rating.
Reacting to the news, French President Nicolas Sarkozy and German Chancellor Angela Merkel issued a statement saying they and their European partners are determined to "take all measures to secure stability in the euro zone."
Earlier, Merkel and Sarkozy agreed plans to impose budget discipline across the euro zone.
Their proposal would penalize governments that fail to keep budget deficits under control. It would also speed up the launch of a permanent bailout fund for euro states in distress.
"We want automatic sanctions in case of non-respect of the rule imposing deficits of less than three percent. And we want that only a qualified majority could oppose itself. That's the opposite of what happens today," Sarkozy said to reporters after his talks in Paris with Merkel.
The proposal would require EU treaty changes and will be put to discussion at an EU summit later this week on December 9.
U.S. Treasury Secretary Timothy Geithner is likely to discuss the proposal when he arrives in Europe later today for talks with financial leaders ahead of the EU summit.
S&P told the governments it would conclude its review "as soon as possible" after the summit.
compiled from agency reports